There are many applications where a quick, efficient way to join lengths of pipe together in a leak proof manner is needed. For example, pipe conveying water to a work site, such as an oil or gas well site, requires couplings between the lengths of pipe. The pipe itself lacks structure for joining one length of pipe to another, so couplings about the exterior of the pipe joints are used.
The prior art has numerous types of couplings. One type of prior art pipe coupling uses a gasket between the adjacent ends of a pipe. A metal band clamps around the gasket and the outside diameter of the pipe, with the band fitting into circumferential grooves in the pipe. Another type of pipe coupling uses an HDPE sleeve over the pipe joint. The sleeve is welded into place with electro-fusion. Still another type of coupling uses a rubber sleeve inside of a rigid shell. The coupling is fit over the pipe joint. Compressed air expands the rubber sleeve around the pipe joint, forming a seal. This type of coupling is exemplified by U.S. Pat. No. 4,026,584.
These prior art couplings either leak, or are too expensive, or are difficult to install.
Furthermore, prior art couplings that use expandable sleeves about the pipe joint may have reduced lifetimes if used on a pipe joint where the end of the pipes are not abutting, but are instead separated by a gap. The sleeve expands into the gap and is subjected to potential damage. U.S. Pat. Nos. 3,420,554 and 3,810,665 disclose a ring to prevent the bladder from entering any gap between the pipe ends, but installing and using the ring is cumbersome.